diff --git a/modules/lang-painless/src/main/java/org/elasticsearch/painless/Compiler.java b/modules/lang-painless/src/main/java/org/elasticsearch/painless/Compiler.java
index 97dddbdfe52c5..e6ed475a7be9f 100644
--- a/modules/lang-painless/src/main/java/org/elasticsearch/painless/Compiler.java
+++ b/modules/lang-painless/src/main/java/org/elasticsearch/painless/Compiler.java
@@ -28,11 +28,14 @@
 import org.objectweb.asm.util.Printer;
 
 import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.security.CodeSource;
 import java.security.SecureClassLoader;
 import java.security.cert.Certificate;
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -89,16 +92,11 @@ final class Loader extends SecureClassLoader {
          */
         @Override
         public Class<?> findClass(String name) throws ClassNotFoundException {
-            if (scriptClass.getName().equals(name)) {
-                return scriptClass;
+            Class<?> found = additionalClasses.get(name);
+            if (found != null) {
+                return found;
             }
-            if (factoryClass != null && factoryClass.getName().equals(name)) {
-                return factoryClass;
-            }
-            if (statefulFactoryClass != null && statefulFactoryClass.getName().equals(name)) {
-                return statefulFactoryClass;
-            }
-            Class<?> found = painlessLookup.canonicalTypeNameToType(name.replace('$', '.'));
+            found = painlessLookup.canonicalTypeNameToType(name.replace('$', '.'));
 
             return found != null ? found : super.findClass(name);
         }
@@ -156,19 +154,14 @@ public Loader createLoader(ClassLoader parent) {
     private final Class<?> scriptClass;
 
     /**
-     * The class/interface to create the {@code scriptClass} instance.
-     */
-    private final Class<?> factoryClass;
-
-    /**
-     * An optional class/interface to create the {@code factoryClass} instance.
+     * The whitelist the script will use.
      */
-    private final Class<?> statefulFactoryClass;
+    private final PainlessLookup painlessLookup;
 
     /**
-     * The whitelist the script will use.
+     * Classes that do not exist in the lookup, but are needed by the script factories.
      */
-    private final PainlessLookup painlessLookup;
+    private final Map<String, Class<?>> additionalClasses;
 
     /**
      * Standard constructor.
@@ -179,9 +172,36 @@ public Loader createLoader(ClassLoader parent) {
      */
     Compiler(Class<?> scriptClass, Class<?> factoryClass, Class<?> statefulFactoryClass, PainlessLookup painlessLookup) {
         this.scriptClass = scriptClass;
-        this.factoryClass = factoryClass;
-        this.statefulFactoryClass = statefulFactoryClass;
         this.painlessLookup = painlessLookup;
+        Map<String, Class<?>> additionalClasses = new HashMap<>();
+        additionalClasses.put(scriptClass.getName(), scriptClass);
+        addFactoryMethod(additionalClasses, factoryClass, "newInstance");
+        addFactoryMethod(additionalClasses, statefulFactoryClass, "newFactory");
+        addFactoryMethod(additionalClasses, statefulFactoryClass, "newInstance");
+        this.additionalClasses = Collections.unmodifiableMap(additionalClasses);
+    }
+
+    private static void addFactoryMethod(Map<String, Class<?>> additionalClasses, Class<?> factoryClass, String methodName) {
+        if (factoryClass == null) {
+            return;
+        }
+
+        Method factoryMethod = null;
+        for (Method method : factoryClass.getMethods()) {
+            if (methodName.equals(method.getName())) {
+                factoryMethod = method;
+                break;
+            }
+        }
+        if (factoryMethod == null) {
+            return;
+        }
+
+        additionalClasses.put(factoryClass.getName(), factoryClass);
+        for (int i = 0; i < factoryMethod.getParameterTypes().length; ++i) {
+            Class<?> parameterClazz = factoryMethod.getParameterTypes()[i];
+            additionalClasses.put(parameterClazz.getName(), parameterClazz);
+        }
     }
 
     /**